Aircraft are commonly equipped with Cabin Pressure Control Systems (CPCSs), which maintain cabin air pressure within a desired range to increase passenger comfort during flight. A typical CPCS may include a controller, an actuator, and an outflow valve. The outflow valve is typically mounted either on a bulkhead of the aircraft or on the outer skin surface of the aircraft, and selectively fluidly couples the aircraft cabin and the atmosphere outside of the aircraft. During operation, the controller commands the actuator to move the outflow valve to various positions to control the rate at which pressurized air is transferred between the aircraft cabin and the outside atmosphere, to thereby control the pressure and/or rate of change of pressure within the aircraft cabin. The controller may be configured to command the actuator to modulate the outflow valve in accordance with a predetermined schedule or as a function of one or more operational criteria. For example, the CPCS may additionally include one or more cabin pressure sensors to sense cabin pressure and supply pressure signals representative thereof to the controller. By actively modulating the outflow valve, the controller may maintain aircraft cabin pressure and/or aircraft cabin pressure rate of change within a desired range.
In some aircraft, the outflow valve may be positioned on the aircraft outer skin surface such that, when pressurized air is exhausted from the cabin, the exhausted air may provide additional forward thrust to the aircraft. Thus, outflow valves may sometimes be referred to as thrust recovery valves. Many thrust recovery valves often include two valve doors with multiple actuation linkages to enable proper sealing, reduce drag, and optimize valve door positioning for cruise thrust creation. In order to maximize the thrust produced by two-door thrust recovery valves, the valve doors are shaped and sealed so that air flow is directed between the doors during flight. As a result, the shapes and cross sections of the valve doors can be relatively complex, as can the seal design.
In addition to the above, because of the pressure load the valve doors may experience during flight, the valve doors are typically manufactured to be relatively robust in strength, which can result in them being relatively thick. Also, because of the relatively large aerodynamic loads during flight, the actuation means for driving the valve doors can be relatively complex, heavy, and expensive. Thus, to provide adequate mechanical advantage, relatively large swing arms may need to be manufactured into both doors.
In some instances, two-door thrust recovery valves are configured such that both doors are actuated by a single actuator. With such valves, both doors are linked together using one or more push rods between the swing arms. Because both doors are actuated together, it can be difficult to ensure that drag is not created by the doors during all modes of flight. This is because while air is directed between the doors, the leading and trailing edges of each door may stick out in the air stream.
Finally, because the thrust recovery valve, when opened on the ground, must provide a maximum exhaust path effective area, and because the doors can be relatively thick and employ swing arms that are large to accommodate the aerodynamic torque, the valve doors are typically relatively large in size. This also results in increased valve weight.
Hence, there is a need for a thrust recovery valve that does not rely on relatively complex shapes and seals, and/or does not rely on a relatively large and expensive actuator to move it, and/or does not create unwanted drag during aircraft cruise operations, and/or can be manufactured from relatively light-weight composite materials. The present invention addresses one or more of these needs.